1. Field of the Invention
The present invention relates generally to a circuit arrangement for reducing the wiring required between discrete signal sources and remote receivers therefor in any military or commercial system using multiple discrete signals.
2. Discussion of the Prior Art
Many discrete electrical signals are used in aircraft and similar complex operating systems. These signals are usually in the form of switch closures to ground or to some DC voltage, and each discrete signal normally requires a minimum of one wire per signal.
In complex electrical/electronic systems such as those aboard an F-14D aircraft, many discrete signals are transmitted from remote switches or various signal sources to other pieces of equipment in the system. These discrete signals are usually in the form of DC voltages or switch closures. In a system of the complexity of the F-14D, for example, a minimum of one wire is required for each discrete signal (if the airframe frame is used as a ground for the signal return). This translates into hundreds of wires routed throughout the aircraft carrying these discrete signals, and each wire adds to the weight and complexity of the aircraft wiring harnesses. In addition, where electromagnetic interference is a consideration, each wire often requires a separate filter therefor for filtering.
To reduce the wiring between units, many signals are now being transmitted over a bus system. In vehicles such as the F-14D aircraft and Trident submarines, this bus system is defined by military specification MIL-STD-1553. The MIL-STD-1553 bus system is a complex pulse-coded system capable of transmitting digital data. However, the MIL-STD-1553 bus requires a digital transmitter at each signal source and a digital receiver at each receiving end. The MIL-STD-1553 bus also requires shielded twisted-pair wires to prevent electromagnetic interferences (EMI). Most MIL-STD-1553 buses also require isolation transformers to couple to each piece of equipment on the bus.